Unraveling Zeolite Heterogeneity and Its Impact on Catalysis

Zeolites exhibit complex structural heterogeneities that critically influence their catalytic behavior, yet these variations remain largely hidden within the crystal lattice. Here, we employ spatially resolved chemical etching combined with a multimodal, multiscale characterization approach to unravel four interrelated forms of heterogeneity in SAPO-34 crystals: defect zoning, silicon zoning, intergrowth zoning, and reactivity zoning. This approach integrates high-resolution SEM and TEM for 3D morphology and internal structure, structured illumination microscopy to map coke distribution on individually tracked crystals, and solid-state NMR (²⁹Si, ¹H, ¹⁹F, hyperpolarized ¹²⁹Xe, and pulsed-field gradient) to probe framework environments, Brønsted acid sites, residual fluoride, micropore accessibility, and diffusion pathways. Using this top-down perspective, we reveal pronounced differences in structural stability among sub-structural units and uncover previously unrecognized X-shaped silicon zoning and an unprecedented CHA-AEI intergrowth structure with complex spatial organization. These coupled heterogeneities collectively govern crystal resistance to chemical etching and active site evolution during methanol-to-olefins conversion, thereby controlling catalytic selectivity and coke formation. This study provides an integrative, multiscale understanding of chemo-structural heterogeneity in zeolites, highlighting the potential of exploiting intrinsic imperfections for the rational design and optimization of advanced catalytic materials.